The present invention relates generally to a computer implemented method, data processing system, and computer program product for exchanging file status information among networked computers. More specifically, the present invention relates to communicating discontinuities in file service to clients of a Network File System (NFS) server.
The Network File System (NFS) is a standard network protocol that makes files stored on a file server accessible to any computer on a network. The NFS client protocol provides access to files that reside on the remote server, in the same way as a client's local file system provides access to files that are stored on a local disk. NFS is transparent to client applications and exposes a traditional file system interface.
The NFS client protocol makes Remote Procedure Calls (RPCs) to the remote server in order to implement access to the files. The interface is implemented by the NFS protocol using RPCs. The RPC layer also provides methods for data representation that are independent of the host architecture. For example, when a client application needs to write to a file that resides in a remote server, it calls a generic write( ) system call. The NFS client protocol implements the write( ) call by invoking a request to the remote server via the RPC layer. RPC marshals the data and parameters of the write( ) call in to a message and encodes the latter in an architecture independent format. The message is sent to the remote host via the TCP/IP protocol stack. The TCP/IP stack of the server delivers the message to the RPC layer, where it is unpacked and passed to the NFS server protocol. The NFS server protocol implements the write( ) operation by accessing the server's local file system. A reply is sent back to the client through the NFS, RPC, and TCP/IP protocol layers.
The RPC layer uses standard external data representation (XDR) for the information exchanged between different computer architectures. NFS on a file server provides a transparent, stateless access to shared data.